Gas reservoir exploitation simulation experiment system and experiment method

Abstract

The invention belongs to the technical field of gas reservoir exploitation, and particularly relates to a gas reservoir exploitation simulation experiment system and method, and the gas reservoir exploitation simulation experiment system comprises a core clamping unit, a pressure injection unit, a carbon dioxide injection unit, a product collection unit and a plurality of pressure detection parts. The experimental rock core is placed in the rock core clamping unit, formation water and gas reservoir gas are injected into the experimental rock core through the pressure injection unit to simulate an initial gas reservoir in the experimental rock core, and formation water is injected into the experimental rock core with initial gas reservoir conditions through the pressure injection unit to simulate the depletion type exploitation process of the initial gas reservoir. Carbon dioxide is injected into the initial gas reservoir subjected to depletion type exploitation through a side injection port in the core holder to perform a simulation experiment for improving the recovery ratio, so that the simulation experiment for improving the recovery ratio by injecting the carbon dioxide into the gas reservoir is realized, and a theoretical technical support is provided for actual exploitation of the gas reservoir.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of gas reservoir exploitation, and particularly relates to a gas reservoir exploitation simulation experiment system and an experiment method. BACKGROUND

[0002] With the increasing demand for energy and the improvement of petroleum engineering technology, the research on volcanic rock oil and gas reservoirs has been increasingly valued and is becoming an important new field of global oil and gas exploration and development. At present, it is generally believed that the reservoir structure and development characteristics of this type of reservoir are different from those of sandstone and carbonate rock oil and gas reservoirs, so there are also great differences in the preparation of development plans and the like. Carbon dioxide storage and enhanced gas recovery technology (CSEGR) can not only restore formation pressure and increase gas reservoir production, but also can seal greenhouse gases in underground traps. At present, the field implementation engineering of carbon capture, utilization and storage (CCUS) combined with oil and gas production increase has begun to be realized in China, but the research and experimental work for gas reservoirs is still in the exploratory stage.

[0003] Carbon dioxide and methane have different physical properties under formation conditions, so they are not easy to mix and enter, but there is currently a lack of physical simulation research on using carbon dioxide to improve gas reservoir recovery. SUMMARY

[0004] The purpose of the present application is to provide a gas reservoir exploitation simulation experiment system and an experiment method, and to realize simulation experiments of carbon dioxide injection for improving the recovery of gas reservoirs.

[0005] In order to achieve the above-mentioned purpose, the present application provides, in one aspect, a gas reservoir exploitation simulation experiment system, comprising:

[0006] a core clamping unit comprising an end part injection inlet, an end part flow outlet, and a plurality of side part injection inlets arranged at intervals along an axial direction;

[0007] a pressure injection unit in communication with the end part injection inlet;

[0008] a carbon dioxide injection unit in selective communication with the plurality of side part injection inlets;

[0009] a product collection unit in communication with the end part flow outlet and used for collecting and measuring the content of the product; and

[0010] a plurality of pressure detection members respectively arranged on pipelines connected with the end part injection inlet, the end part flow outlet and the side part injection inlets.

[0011] In some embodiments, the core clamping unit comprises:

[0012] a core holder having an end injection port and an end flow outlet formed at two axial ends thereof respectively, and a side wall of the core holder forming a plurality of side injection ports;

[0013] an angle adjuster connected to the core holder and used to adjust an angle of a central axis of the core holder.

[0014] In some embodiments, the production collection unit comprises:

[0015] a gas-liquid separation device comprising one inlet and two outlets, the inlet being connected to the end flow outlet pipeline;

[0016] a liquid metering device connected to one of the outlets and used to meter liquid content; and

[0017] a gas chromatograph connected to the other outlet and used to display gas content variation.

[0018] In some embodiments, the plurality of side injection ports comprises at least a first side injection port arranged close to the end injection port, a second side injection port arranged close to the end flow outlet, and a third side injection port arranged between the first and second side injection ports.

[0019] In some embodiments, the gas reservoir exploitation simulation experiment system further comprises a check valve arranged on a pipeline between the end flow outlet and the production collection unit, and the pressure detecting member arranged on the pipeline connected to the end flow outlet is arranged on a pipeline between the check valve and the end flow outlet.

[0020] The second aspect of the present application provides a gas reservoir exploitation simulation experiment method, comprising:

[0021] preparing an experimental core and constructing an initial gas reservoir in the experimental core;

[0022] pumping formation water into an injection end of the experimental core with the initial gas reservoir to deplete the initial gas reservoir;

[0023] injecting carbon dioxide into a side of the experimental core after depletion;

[0024] collecting production from an outflow end of the experimental core and analyzing the production.

[0025] In some embodiments, the gas reservoir exploitation simulation experiment method further comprises:

[0026] inclining and fixing the experimental core with the initial gas reservoir and setting an angle of a central axis of the experimental core to a formation angle.

[0027] In some embodiments, pumping formation water into the injection end of an experimental core containing an initial gas reservoir to deplete the initial gas reservoir includes:

[0028] Set the initial pressure at the outflow end of the experimental core and the preset pressure after depletion mining.

[0029] The real-time pressure at the outflow end of the experimental core was detected;

[0030] Injecting carbon dioxide into the side of the experimental core after depletion mining includes:

[0031] After determining that the real-time pressure has reached the preset pressure, carbon dioxide is injected into the side of the experimental core after depletion mining.

[0032] In some embodiments, a gas-water boundary is formed inside the experimental core into which formation water is pumped, and carbon dioxide is injected into the side of the experimental core after depletion mining, comprising:

[0033] Determine the gas injection area according to experimental needs;

[0034] The gas injection location on the side of the experimental core after depletion mining is determined based on the gas injection area, and carbon dioxide is injected at a constant rate from the gas injection location.

[0035] The gas injection area includes an outer edge zone, an inner edge zone, and an upper edge zone. The outer edge zone and the inner edge zone are located on opposite sides of the gas-water boundary. The outer edge zone is close to the injection end of the experimental core, the inner edge zone is relatively far from the injection end of the experimental core, and the upper edge zone is located on the gas-water boundary.

[0036] In some embodiments, collecting the products flowing out from the outflow end of the experimental core includes:

[0037] Separate the liquid and gas phases of the product;

[0038] The separated gas phase is subjected to compositional analysis, and the gas phase with the same composition as the initial gas reservoir is quantified;

[0039] The separated liquid phase is metered;

[0040] Calculate the recovery rate of the initial gas reservoir.

[0041] Through the above technical solutions, the gas reservoir development simulation experimental system and experimental method provided in this application have the following beneficial effects:

[0042] First, the experimental core is placed into the core clamping unit; second, the gas reservoir gas is injected into the experimental core by using the pressure injection unit to saturate the experimental core to form an initial gas reservoir; then, the formation water is injected into the experimental core by using the pressure injection unit to deplete the initial gas reservoir; then, the carbon dioxide is injected into the experimental core through the corresponding side injection port according to the need; finally, the simulation experiment is completed when the carbon dioxide concentration collected by the production collection unit reaches the preset concentration. In the present application, the initial gas reservoir in the experimental core is simulated by injecting the formation water and the gas reservoir gas into the experimental core through the pressure injection unit, the depletion process of the initial gas reservoir is simulated by injecting the formation water into the experimental core with the initial gas reservoir condition through the pressure injection unit, and the enhanced recovery simulation experiment is performed by injecting the carbon dioxide into the initial gas reservoir after the depletion through the side injection port on the core holder, so as to realize the simulation experiment of the carbon dioxide injection into the gas reservoir for enhanced recovery, and further provide theoretical and technical support for the actual exploitation of the gas reservoir.

[0043] Other features and advantages of the embodiments of the present application will be described in detail in the following detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0044] The accompanying drawings are included to provide a further understanding of the embodiments of the present application, and constitute a part of the specification, and are used to explain the embodiments of the present application together with the following detailed description, but do not constitute a limitation of the embodiments of the present application. For those skilled in the art, other drawings can be obtained from the structures shown in the drawings without creative labor. In the drawings:

[0045] Figure 1 It is a structure schematic diagram of the gas reservoir exploitation simulation experiment system according to the specific embodiments of the present application;

[0046] Figure 2 It is a step diagram of the gas reservoir exploitation simulation experiment method according to the specific embodiments of the present application;

[0047] Figure 3 It is a schematic diagram of the first curve of the depletion corresponding to different preset pressures according to the exemplary embodiments of the present application;

[0048] Figure 4 It is a schematic diagram of the recovery rate change curve with time corresponding to different preset pressures according to the exemplary embodiments of the present application.

[0049] LEGEND OF DRAWINGS

[0050] 100, gas reservoir exploitation simulation experiment system; 1, angle adjuster; 2, core holder; 21, side injection port; 3, pressure injection unit; 31, first pressure pump; 32, first container; 4, carbon dioxide injection unit; 5, product collection unit; 51, gas-liquid separation device; 52, liquid metering device; 53, gas chromatograph; 6, first pressure detection piece; 7, second pressure detection piece; 8, third pressure detection piece; 9, check valve. DETAILED DESCRIPTION

[0051] The specific embodiments of the present application are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present application, and are not intended to limit the present application.

[0052] The gas reservoir exploitation simulation experiment system 100 and the experimental method according to the present application are described below with reference to the accompanying drawings.

[0053] As shown in Figure 1 The specific embodiments of the present application provide a gas reservoir exploitation simulation experiment system 100, which comprises a core holding unit, a pressure injection unit 3, a carbon dioxide injection unit 4, a product collection unit 5, and a plurality of pressure detection pieces. The core holding unit comprises an end injection port, an end flow outlet, and a plurality of side injection ports 21 arranged at intervals along the axial direction. The pressure injection unit 3 is in communication with the end injection port. The carbon dioxide injection unit 4 is in communication with the plurality of side injection ports 21 selectively. The product collection unit 5 is in communication with the end flow outlet and is used to collect and meter the content of the product. The plurality of pressure detection pieces are respectively arranged on the pipelines connected with the end injection port, the end flow outlet, and the side injection ports 21.

[0054] In order to realize the simulation experiment of injecting carbon dioxide into the gas reservoir to improve the recovery rate, firstly, the initial gas reservoir in the rock mass needs to be simulated, secondly, the initial gas reservoir in the rock mass needs to be depleted, then, when the gas pressure of the initial gas reservoir in the rock mass is reduced to the depletion pressure, carbon dioxide is injected into the rock mass, and finally, when the carbon dioxide concentration in the product reaches the critical value, the injection of carbon dioxide is stopped. In the present application, the experimental core is placed in the core clamping unit as the rock mass, the initial gas reservoir in the experimental core is simulated by injecting formation water and gas reservoir gas into the experimental core through the pressure injection unit 3, the depletion process of the initial gas reservoir is simulated by injecting formation water into the experimental core through the pressure injection unit 3, and the gas pressure value of the initial gas reservoir in the depletion process is detected by the pressure detection piece; the carbon dioxide is injected into the initial gas reservoir after the depletion through the side injection inlet 21 on the core holder 2 to improve the recovery rate, and the carbon dioxide concentration in the product is detected by the product collection unit 5. It can be seen that the gas reservoir exploitation simulation experiment system 100 provided by the embodiment of the present application can realize the simulation experiment of injecting carbon dioxide into the gas reservoir to improve the recovery rate, thereby providing theoretical technical support for the actual exploitation of the gas reservoir.

[0055] In some embodiments, the core clamping unit includes a core holder 2 and an angle adjuster 1, wherein the two ends of the core holder 2 in the axial direction respectively form an end injection inlet and an end flow outlet, and the side wall of the core holder 2 forms a plurality of side injection inlets 21; the angle adjuster 1 is connected with the core holder 2 and is used to adjust the central axis inclination angle of the core holder 2.

[0056] Specifically, the core holder 2 has a cavity inside for accommodating the experimental core, and the size of the cavity can be adjusted to be suitable for experimental cores of different specifications; the other soil around the soil body forming the gas reservoir also exerts soil pressure, and the core holder 2 can also adjust the pressure of the cavity wall on the experimental core to adjust the confining pressure of the experimental core. The above settings can improve the reliability of the gas reservoir exploitation simulation experiment system 100. The size, structure and the way of adjusting the size of the cavity of the core holder 2 are well known to those skilled in the art, and do not belong to the core of the present application, which will not be described here.

[0057] Further, the core clamping unit further includes a temperature adjuster connected with the core holder 2 and a temperature sensor arranged in the cavity of the core holder 2, the temperature adjuster is used to adjust the temperature of the core holder 2, and the temperature sensor is used to feedback the temperature of the experimental core in the cavity of the core holder 2, so as to adjust the temperature of the experimental core installed in the cavity of the core holder 2, and further realize the simulation of the formation temperature to improve the accuracy of the experimental results.

[0058] In fact, the soil body with gas reservoir has various postures, i.e. has different formation dip angles. In the present application, the angle adjuster 1 connected with the core holder 2 is arranged to adjust the central axis dip angle of the core holder 2, so as to adjust the central axis dip angle of the experimental core in the core holder 2, and further simulate the gas reservoir with different formation dip angles to make the experimental core closer to the actual situation and improve the reliability of the gas reservoir exploitation simulation experiment system 100.

[0059] Those skilled in the art can understand that the angle adjuster 1 can be selected as a rotating mechanism connected with the middle part of the core holder 2, or can be selected as a lifting mechanism connected with the axial two ends of the core holder 2, as long as the mechanism can realize the change of the central axis dip angle of the core holder 2, which all belong to the protection scope of the present application.

[0060] In some embodiments, the pressure injection unit 3 includes a first pressure pump 31 and a first container 32 connected with each other, the first container 32 is connected with the injection end pipeline of the core holder 2, and the first container 32 is used to fill the substance needed to be injected into the experimental core. In order to avoid the mutual influence between the substances, different first containers 32 are connected with the injection pump when different substances are injected. The carbon dioxide injection unit 4 includes a second pressure pump and a second container, the second container is filled with carbon dioxide and is connected with the side injection inlet 21 of the core holder 2. The first pressure pump 31 and the second pressure pump can adjust the injection speed by adjusting the pressure, so as to meet the experimental conditions.

[0061] In some embodiments, the production collection unit 5 includes a gas-liquid separation device 51, a liquid metering device 52 and a gas chromatography device 53. The gas-liquid separation device 51 includes one feeding port and two discharging ports, the feeding port is connected with the end outlet pipeline; the liquid metering device 52 is connected with one of the discharging ports and is used to meter the liquid content; and the gas chromatography device 53 is connected with the other discharging port and is used to display the gas content change.

[0062] The production is the substance flowing out from the end outlet during the whole simulation experiment, including the formation water, the gas reservoir gas and the carbon dioxide gas, i.e. the production includes the substances in the gas phase and the liquid phase, and the contents of the gas phase and the liquid phase need to be metered. In the present application, the gas-liquid separation device 51 is used to separate the gas phase and the liquid phase of the production, and the separated gas phase and liquid phase flow out from two different discharging ports to the liquid metering device 52 and the gas chromatography device 53, so as to realize the metering and analysis of the production. The size and structure of the gas-liquid separation device 51 are well known to those skilled in the art, and do not belong to the core of the present application, and are not described here.

[0063] The gas chromatograph 53 is used to qualitatively and quantitatively analyze a complex mixture of multiple components by using chromatographic separation technology and detection technology, and finally form an analysis chromatogram with different chromatographic peaks, each chromatographic peak corresponds to a substance, and the specific structure and principle are well known to those skilled in the art and do not belong to the core of the present application. Here is not described.

[0064] Those skilled in the art can understand that the liquid metering device 52 can be selected from a measuring cylinder, a measuring cup, an electronic scale, and other instruments capable of measuring the volume or mass of a liquid phase, and all belong to the protection scope of the present application. The structure and principle of the gas chromatograph 53 are well known to those skilled in the art and do not belong to the core of the present application. Here is not described.

[0065] In some embodiments, the gas reservoir exploitation simulation experiment system 100 further comprises a check valve 9 arranged on the pipeline between the end flow outlet and the production collection unit 5, which is used to prevent the backflow of the material flowing out of the end flow outlet, that is, only allows the material to flow in one direction.

[0066] It should be noted that the pressure detection member arranged on the pipeline connected with the end flow outlet is located on the pipeline between the check valve 9 and the end flow outlet, thereby preventing the check valve 9 from affecting the detection result of the pressure detection member, and further improving the reliability of the gas reservoir exploitation simulation experiment system 100. The structure of the check valve 9 is well known to those skilled in the art and does not belong to the core of the present application. Here is not described.

[0067] In some embodiments, the plurality of side injection inlets 21 at least comprises a first side injection inlet 21 arranged near the end injection inlet, and a second side injection inlet 21 arranged near the end flow outlet, and a third side injection inlet 21 located between the first side injection inlet 21 and the second side injection inlet 21.

[0068] In the actual gas reservoir exploitation process, the formation water is located below the gas reservoir and forms a gas-water interface, the gas-water interface has a certain thickness and tends to be stable during the exploitation process, and the gas-water interface is parallel to the horizontal plane of the formation water in the stable state. Generally, when the gas pressure or water pressure fluctuates little, the gas-water interface is in a stable state. In other words, after the gas reservoir is depleted to a preset value, the gas-water interface is in a stable state.

[0069] At this time, carbon dioxide needs to be injected to improve the recovery efficiency of the gas reservoir, but the gas injection area needs to be determined before injecting carbon dioxide. The gas injection area is divided based on the gas-water interface, wherein the area below the gas-water interface is the outer area, that is, the formation water area; the area above the gas-water interface is the inner area, that is, the gas reservoir area; and the area on the gas-water interface is the upper area.

[0070] In the present application, by arranging the third side injection port 21 in alignment with the gas-water boundary, and by arranging the first side injection port 21 and the second side injection port 21 in alignment with the formation water region and the gas reservoir region respectively, selective injection of gas into the inboard region, the on-board region and the off-board region can be achieved according to the experimental requirements, thereby simulating the influence of different injection positions of carbon dioxide on the improvement of the recovery rate of gas reservoir exploitation, so as to improve the practicability of the gas reservoir exploitation simulation experiment system 100.

[0071] As shown in Figure 2 the specific embodiments of the present application also provide a gas reservoir exploitation simulation experiment method, which comprises:

[0072] S1: preparing an experimental core and constructing an initial gas reservoir in the experimental core;

[0073] S2: pumping formation water into the injection end of the experimental core with the initial gas reservoir to deplete the initial gas reservoir;

[0074] S3: injecting carbon dioxide into the side of the experimental core after depletion;

[0075] S4: collecting the production from the outflow end of the experimental core and analyzing the production.

[0076] It should be noted that step S4 is performed simultaneously after step S2 starts and continues until the experiment ends, and steps S1, S2, S3 and S4 can be performed by means of the above-mentioned gas reservoir exploitation simulation experiment device. The following exemplary embodiments of the present application will be described by using the gas reservoir exploitation simulation experiment device to perform the gas reservoir exploitation simulation experiment method. In the exemplary embodiments of the present application, the initial gas reservoir is a resource gas such as methane gas that is insoluble in water. Since the gas reservoir exploitation simulation experiment method adopts all embodiments of the gas reservoir exploitation simulation experiment device, the gas reservoir exploitation simulation experiment method has all the beneficial effects brought by the gas reservoir exploitation simulation experiment device.

[0077] Before starting the gas reservoir exploitation simulation experiment method, first, the connection of the gas reservoir exploitation simulation experiment device needs to be performed, then the connectivity and sealing of the pipelines and valves of the gas reservoir exploitation simulation experiment device are detected, and the dead volume of the pipelines and valves is measured. It should be noted that the detection of connectivity and sealing is well known to those skilled in the art and does not belong to the core of the present application, so it will not be described here.

[0078] Specifically, a first pipeline is arranged between the pressure injection unit 3 and the end injection port of the core holder 2, and a first pressure detection member 6 and a first valve body are arranged on the first pipeline; a second pipeline is arranged between the production collection unit 5 and the end flow port of the core holder 2, and a second pressure detection member 7 and a second valve body are arranged on the second pipeline; a third pipeline is arranged between the carbon dioxide injection unit 4 and the side injection port 21, and a third pressure detection member 8 and a third valve body are arranged on the third pipeline. The first valve body and the third valve body are on-off valves, and the second valve body is a check valve 9.

[0079] In some embodiments, the step S1 comprises:

[0080] S11: selecting a plurality of core samples to form an experimental core in series;

[0081] S12: cleaning the experimental core;

[0082] S13: injecting formation water into the cleaned experimental core to saturate the experimental core;

[0083] S14: injecting gas reservoir gas into the experimental core saturated with the formation water to form an initial gas reservoir;

[0084] In the step S11, the sizes of the selected core samples are consistent, and the plurality of core samples are connected in series along the axial direction. Since the experimental core is formed by connecting the plurality of core samples in series, the percolation channels in the experimental core are formed by the percolation channels in each experimental core being connected to each other. The pores in adjacent experimental cores will inevitably cause the percolation channels to be discontinuous, thereby changing the flow properties of the experimental core, and further affecting the accuracy of the experiment. The change in the flow properties caused by the discontinuity of the percolation channels is referred to as "end effect".

[0085] To reduce the influence of the end effect on the accuracy of the experiment, in the specific embodiments of the present application, filter paper is arranged on the contact surface of adjacent core samples, and the connection order of the plurality of core samples is determined according to the harmonic mean principle. The harmonic mean principle refers to first calculating the first average permeability of all core samples; then taking the core sample closest to the average permeability among all core samples as the first core sample and placing it in the first position; then calculating the second average permeability of the remaining core samples, and taking the core sample closest to the second average permeability among the remaining core samples as the second core sample and placing it in the second position, and so on, to determine the arrangement order of each core sample.

[0086] Before the step S12, the step S13 and the step S14, the experimental core is put into the cavity of the core holder 2, and the experimental sample is set with confining pressure by using the core holder 2, and then the end outlet and the side injection inlet 21 of the core holder 2 are closed, and the vacuumization is performed through the end injection inlet of the core holder 2, so that the experimental core can simulate the formation condition.

[0087] In fact, the soil with the gas reservoir has various postures, i.e. has different formation inclinations, and in some embodiments, the gas reservoir exploitation simulation experiment method further comprises: inclining and fixing the experimental core with the initial gas reservoir and making the central axis of the experimental core have the formation inclination. In the present application, the central axis of the core holder 2 is adjusted by setting the angle adjuster 1 connected with the core holder 2, so as to adjust the central axis of the experimental core in the core holder 2, and further simulate the gas reservoir with different formation inclinations, so that the experimental core is closer to the actual situation.

[0088] After the experimental core is put into the core holder 2, the step S12 is performed to clean the experimental core, specifically including: firstly connecting the first container 32 containing the petroleum ether and the ethanol to the first pipeline and opening the first pressure pump 31 to inject the petroleum ether and the ethanol into the experimental core; then connecting the empty first container 32 to the first pipeline and opening the first pressure pump 31 to blow dry gas into the experimental core; finally, performing the vacuumization on the inside of the experimental core.

[0089] In the present application, the experimental core is cleaned by injecting the petroleum ether and the ethanol, so as to reduce the influence of impurities on the purity of the injected substances; the experimental core is dried by blowing the dry gas, so as to accelerate the volatilization of the petroleum ether and the ethanol; the residual impurities in the experimental core are removed by the vacuumization, so as to avoid the influence of the impurities on the purity of the injected substances. It can be seen that the influence of the impurities on the experiment can be obviously reduced by the step S12, and the reliability of the experimental results is improved.

[0090] After the first container 32 containing the formation water is connected to the first pipeline, the temperature adjuster is used to increase the temperature of the experimental core, and when the temperature sensor detects that the temperature of the experimental core reaches the formation temperature, the first pressure pump 31 is started to inject the formation water into the experimental core until the experimental core reaches the saturation state and the injection is stopped; when the formation water in the experimental core reaches the saturation state, the first container 32 containing the gas reservoir gas is connected to the first pipeline, and the first pressure pump 31 is started to inject the gas reservoir gas into the experimental core until the first pressure detection piece 6 on the first pipeline reaches the injection pressure and the injection is stopped after being stable for more than 6 hours. It can be seen that the influence of the impurities on the experiment can be obviously reduced by the step S12, and the reliability of the experimental results is improved.

[0091] In some embodiments, the step S2 comprises:

[0092] S21: set an initial pressure of an outflow end of the experimental core and a preset pressure after depletion production;

[0093] detect a real-time pressure of the outflow end of the experimental core;

[0094] S22: pump formation water into an injection end of the experimental core with an initial gas reservoir

[0095] S23: detect a real-time pressure of the outflow end of the experimental core;

[0096] S24: calculate a recovery rate of the gas reservoir gas.

[0097] Specifically, the first container 32 filled with the formation water is connected with the first pipeline, and a reading of the second pressure detection member 7 on the second pipeline is read in real time, i.e., a real-time pressure, which gradually decreases from an initial pressure to a preset pressure during the depletion production, and when the real-time pressure decreases to the preset pressure, the depletion production of the initial gas reservoir in the experimental core is completed.

[0098] Further, during the depletion production, the production time is recorded in real time, and the recovery rate of the produced gas reservoir gas is calculated, so that the production time and the recovery rate are correspondingly plotted into a first curve, so as to intuitively obtain the change of the recovery rate with the production time.

[0099] wherein the gas reservoir gas content after the gas-liquid separation device 51 is read by the gas chromatograph device 53, and the recovery rate is a percentage of the gas reservoir gas amount to the initial gas reservoir amount, which increases with time, but the increasing rate of the recovery rate gradually slows down.

[0100] It should be noted that the first injection pump for pumping the formation water needs to maintain a constant pressure to gradually stabilize the gas reservoir gas and form a gas-water interface, which is parallel to the horizontal plane of the formation water, and the position of the gas-water interface can be adjusted by adjusting the size of the constant pressure. Generally, the position of the gas-water interface is kept aligned with the third side injection inlet 21 of the core holder 2, so that the first side injection inlet 21 and the second side injection inlet 21 are respectively arranged in the formation water region and the gas reservoir region, so as to simulate the influence of different gas injection regions on improving the recovery rate of the gas reservoir production, thereby improving the practicability of the gas reservoir production simulation experiment.

[0101] In some embodiments, step S3 comprises:

[0102] S31: determining a gas injection region according to experimental needs;

[0103] S32: determining the injection position of the carbon dioxide on the side of the experimental core after the depletion development according to the injection area, and connecting the second container filled with carbon dioxide with the corresponding side injection inlet 21 pipeline;

[0104] S33: opening the second pressure pump to inject carbon dioxide after the real-time pressure reaches the preset pressure.

[0105] Wherein, the injection area is divided into edge-out area, edge-in area and edge-on area based on the gas-water interface. The edge-out area is below the gas-water interface, which is the formation water area; the edge-in area is above the gas-water interface, which is the gas reservoir area; the edge-on area is on the gas-water interface. The edge-out area is close to the injection end of the experimental core, the edge-in area is relatively far from the injection end of the experimental core, and the edge-on area is on the gas-water boundary.

[0106] It should be noted that during the injection of carbon dioxide, the first pressure pump 31 always maintains a constant pressure state to maintain the stability of the gas-water interface, and the second pressure pump is adjusted to inject carbon dioxide at a constant speed.

[0107] In some embodiments, step S4 comprises:

[0108] S41: separating the liquid phase and the gas phase of the output;

[0109] S42: detecting the composition of the separated gas phase and measuring the gas phase with the same composition as the initial gas reservoir;

[0110] S43: measuring the separated liquid phase;

[0111] S44: calculating the recovery rate of the initial gas reservoir.

[0112] Specifically, after injecting carbon dioxide gas, the output of the formation water, the gas reservoir gas and the carbon dioxide will flow into the gas-liquid separation device 51 from the outflow end of the core holder 2 through the second pipeline; secondly, after the action of the gas-liquid separation device 51, the liquid phase in the output flows into the liquid measuring device 52, and the gas phase in the output flows into the gas chromatograph device 53, so as to measure the formation water content, the carbon dioxide content and the gas reservoir gas content of the output respectively; finally, the displacement efficiency of carbon dioxide is calculated.

[0113] Further, the formation water content is read by the liquid measuring device 52, the carbon dioxide content and the methane content (gas reservoir gas content) are read by the gas chromatograph device 53, and the displacement efficiency of carbon dioxide is the percentage of the output methane content to the initial gas reservoir methane in the experimental core, which is equivalent to the recovery rate.

[0114] At the same time, the displacement time is recorded, so as to draw a second curve corresponding to the displacement time and the displacement efficiency, so as to intuitively obtain the change of the displacement efficiency with the displacement time.

[0115] The displacement time continues the depletion production time record until the percentage of carbon dioxide in the production output reaches a critical value, generally above 90%, and then the record is stopped.

[0116] Finally, the first curve and the second curve are drawn together to obtain a recovery rate curve with time, so that the effect of injecting carbon dioxide on the recovery rate is clearly seen, thereby providing theoretical and technical support for the actual production of gas reservoirs.

[0117] Those skilled in the art can understand that each experiment can obtain a different recovery rate curve with time by changing the preset pressure of depletion production and the injection position of injected carbon dioxide, thereby obtaining the influence of different factors on gas reservoir production, and thereby providing more comprehensive theoretical and technical support.

[0118] In the exemplary embodiments of the present application, the experimental gas is carbon dioxide gas with a purity of more than 99% and methane gas with a purity of 99%; the formation water used is prepared according to the actual situation of the target block; the initial pressure of depletion production is 40 MPa; the preset pressures of depletion production are selected as 30 MPa, 20 MPa, 15 MPa and 10 MPa respectively; the injection speed of carbon dioxide is 0.2 mL / min; and the critical value of carbon dioxide is 95%.

[0119] As shown in Figure 3 and Figure 4 After four experiments are performed at the same injection position, different recovery rate curves with time corresponding to different preset pressures are obtained, and according to the analysis of the curves, it is obtained that the recovery rate can still be increased by 14.21% after injecting carbon dioxide when the preset pressure reaches 10 MPa, thereby obtaining that the injection of carbon dioxide after depletion production to 10 MPa can maximize the recovery rate of methane gas.

[0120] In the description of the present application, it should be understood that the terms "first" and "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first" and "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0121] In this application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting", "fixing" and the like should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection or communication with each other; can be directly connected, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0122] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. Furthermore, the skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0123] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A gas reservoir development simulation experimental system, characterized in that, include: The core clamping unit includes an end injection port, an end outlet, and multiple side injection ports arranged at intervals along the axial direction (21); The pressure injection unit (3) is connected to the end injection port; The carbon dioxide injection unit (4) is selectively connected to one of the plurality of side injection ports (21); The product collection unit (5) is connected to the end outlet and is used to collect and measure the product content; and, Multiple pressure detection devices are respectively installed on the pipeline connected to the end injection port, the end outlet and the side injection port (21).

2. The gas reservoir development simulation experimental system according to claim 1, characterized in that, The core clamping unit includes: The core holder (2) has an end inlet and an end outlet formed at both ends along the axial direction, and the sidewalls of the core holder (2) form a plurality of side inlets (21); and An angle adjuster (1) is connected to the core holder (2) and is used to adjust the tilt angle of the central axis of the core holder (2).

3. The gas reservoir development simulation experimental system according to claim 1, characterized in that, The output collection unit (5) includes: The gas-liquid separation device (51) includes a feed inlet and two discharge outlets, wherein the feed inlet is connected to the end outlet pipe; Liquid metering device (52), connected to one of the outlet pipes and used for metering liquid content; and A gas chromatograph (53) is connected to another outlet pipe and is used to display changes in gas content.

4. The gas reservoir development simulation experimental system according to claim 1, characterized in that, The plurality of side injection ports (21) include at least a first side injection port (21) disposed near the end injection port, a second side injection port (21) disposed near the end outlet, and a third side injection port (21) located between the first side injection port (21) and the second side injection port (21).

5. The gas reservoir development simulation experimental system according to claim 1, characterized in that, The gas reservoir development simulation experimental system (100) also includes a check valve (9), which is installed on the pipeline between the end outlet and the product collection unit (5). The pressure detection element installed on the pipeline connected to the end outlet is located on the pipeline between the check valve (9) and the end outlet.

6. A method for simulating gas reservoir development, characterized in that, include: Prepare experimental cores and construct an initial gas reservoir within the experimental cores; Formation water is pumped into the injection end of the experimental core containing the initial gas reservoir to exhaust the initial gas reservoir. Carbon dioxide was injected into the side of the experimental core after depletion mining. The products flowing out from the outflow end of the experimental core were collected and analyzed.

7. The gas reservoir development simulation experiment method according to claim 1, characterized in that, The gas reservoir development simulation experiment method also includes: The experimental core containing the initial gas reservoir is tilted and fixed so that the dip angle of the central axis of the experimental core is the formation dip angle.

8. The gas reservoir development simulation experiment method according to claim 1, characterized in that, Pumping formation water into the injection end of an experimental core containing an initial gas reservoir to deplete the initial gas reservoir includes: Set the initial pressure at the outflow end of the experimental core and the preset pressure after depletion mining. The real-time pressure at the outflow end of the experimental core was detected; Injecting carbon dioxide into the side of the experimental core after depletion mining includes: After determining that the real-time pressure has reached the preset pressure, carbon dioxide is injected into the side of the experimental core after depletion mining.

9. The gas reservoir development simulation experiment method according to claim 1, characterized in that, A gas-water boundary is formed inside the experimental core into which formation water is pumped. Injecting carbon dioxide into the side of the experimental core after depletion mining includes: Determine the gas injection area according to experimental needs; The gas injection location on the side of the experimental core after depletion mining is determined based on the gas injection area, and carbon dioxide is injected at a constant rate from the gas injection location. The gas injection area includes an outer edge zone, an inner edge zone, and an upper edge zone. The outer edge zone and the inner edge zone are located on opposite sides of the gas-water boundary. The outer edge zone is close to the injection end of the experimental core, the inner edge zone is relatively far from the injection end of the experimental core, and the upper edge zone is located on the gas-water boundary.

10. The gas reservoir development simulation experiment method according to claim 1, characterized in that, The products collected from the outflow end of the experimental core include: Separate the liquid and gas phases of the product; The separated gas phase is subjected to compositional analysis, and the gas phase with the same composition as the initial gas reservoir is quantified; The separated liquid phase is metered; Calculate the recovery rate of the initial gas reservoir.

Images